Some local files won't sync to Android

[Dylacam]

Plan

Premium

Country

USA

Device

Motorola Moto G7

Operating System

Android 9

My Question or Issue

I have some audio files from CDs and such that are not on Spotify and thus I must use the "local files" ability on desktop to put them in playlists. This works just fine on my PC but when I attempt to sync them to my phone (an android) not all of the songs are playable. Instead, some of the songs show up as downloaded and playable but no audio comes out and if I pause them the progress bar resets. But some songs synced at the same time are just fine. I cannot find any common theme between the problem songs, it appears random to me. All the songs are mp3s and work fine on desktop.

I have tried restarting, updating, and undownloading/redownloading on both my PC and my phone but the same songs have the same problem.